1. Field of the Invention
This invention relates to a surface treatment method of a copper foil with a silane coupling agent. More particularly, this invention relates to a surface treatment method of a copper foil including coating the surface of the copper foil with a mixture of 3-aminopropyltriethoxy silane and vinyltriethoxysilane to increase adhesion of the surface of the copper foil to an insulating substrate.
2. Description of the Related Art
It is common that inorganic materials such as metal are bonded with organic materials such as rubber and resin as seen in printed circuit boards (PCBs). PCB is fabricated by adhering a copper foil to a substrate with mechanical and chemical process to make insulating resin-impregnated substrate with necessary patterns.
Printed circuits are widely used in various industrial electronic/electric devices such as communication equipments and all sorts of control devices in addition to various household appliances, such as radios, televisions, washing machines, audios, microwave oven and VTR. In early stage, single side PCB was conventionally used, but nowadays multi-layer PCB, double side PCB and the like are additionally used.
In recent years, as the electronic/electric devices are more and more slim and compact, the PCBs are required to be finer, smaller and more concentrated than ever. Hence, the high quality electrolytic copper foil is needed in manufacturing of substrates and printed circuits. The insulating substrates usually used for the industrial printed circuits are prepreg made of epoxy resin in which glass fiber is impregnated. In general, the PCB is obtained by the process comprising bonding a electrolytic copper foil used for printed circuit to a insulating substrate under the high temperature and high pressure and then etching the copper foil according to the circuit design.
As the copper foil-bonded substrates go through a few of hot pressing and heat treatment process, the adhesion of copper foil to resin may be deteriorated due to heat shock, rust or stain which may occur during mechanical and chemical process and undercutting phenomenon caused by etching. Hence, the adhesion of copper foil to the insulating substrate may be degraded. Therefore, a number of the method of coating the metal surface by another kind of metal for improving adhesion are suggested.
For example, U.S. Pat. No. 3,293,109 discloses a surface treatment method for increasing mechanical adhesion of copper foil by forming copper nodules on a surface of the copper foil and then coating the nodularized-surface. Korean patent publication No. 83-2611 discloses a method of forming zinc layer containing tin and vanadium on copper foil. Korean patent publication No. 84-1643 discloses a method of forming phosphorous nickel layer on copper foil. Korean patent publication No. 87-692 discloses a method of forming nickel layer containing sulfur, phosphorus and arsenic on copper foil. Japanese patent publication S51-35711 discloses a method of conducting rust-preventing treatment using electrolytic chromate after barrier surface treatment on the surface of copper. But all of above-mentioned processes are proposed to improve adhesion of copper foil layer to insulation substrate with mechanical method. Therefore, these processes are not the efficient methods to inhibit copper ions' diffusion towards resin layer during heat process and weak adhesion caused by alloying element effect during chemical treatment.
Furthermore, these processes have limitations in the matter of improving adhesion of metal as inorganic material to polymer as organic material.